Brigadier General Saddam Hussein al-Dhahri, the head of security of the presidential palace, was killed by an attacker from a passing car as the victim left work in the southern Yemeni city of Taiz, a security source told the Reuters news agency.

In a separate incident, Police Colonel Abdullah Gaithallah was killed in the southern province of al-Baida by gunmen who ambushed his car.

It was not immediately known who the gunman were, but Yemeni officials have blamed a string of similar killings of police and military officers on armed rebels affiliated to al-Qaeda.

Violence is common in Yemen, where an interim government is facing southern secessionists and northern Houthi rebels in addition to the al-Qaeda-linked fighters who are seeking to overthrow the government and impose Islamic law.